The present invention relates to syringes of the type which are used for injection of pharmaceuticals into patients and sometimes for withdrawing liquid samples from patients. More particularly, the present invention relates to the provision of an improved syringe constructed such that, once it has been used, it can be easily manipulated to retract the rather sharp cannula to be entirely disposed within the barrel of the syringe in a point protective position. The manipulation of the cannula breaks the syringe barrel such that the syringe cannot thereafter be used.
With the threat of AIDS and hepatitis infection becoming a major concern, medical personnel must take extra precautions not to prick themselves with the cannula point of a syringe, particularly a syringe which has been used on a patient. Presently, once a syringe is used, medical personnel are required very carefully to place a protective cover back over the cannula or to drop the syringe into a "safe depository" system. This act of replacing the protective cover back over the cannula is dangerous. Further, it is difficult and expensive to provide safe depository systems at all locations where syringes are used.
It is known to provide a syringe having features designed to protect users from inadvertent needle pricks or other harm. See, for instance, U.S. Pat. Nos. 2,473,733; 2,888,923; 2,925,083; 2,972,991; 3,306,290; 3,356,089; 3,820,652; 4,026,287; 4,507,117; 4,592,744; 4,692,156; 4,710,170; 4,747,830; 4,790,822; and 4,804,370.
Our inventive syringe, however, is the first syringe designed to have a frangible end wall portion or an end wall means connected to the syringe barrel by a frangible portion such that continued movement of the plunger after the syringe contents are expelled with a predetermined higher force application will break the frangible portion to separate the cannula from the barrel so that the cannula can then be retracted into the barrel.
It is an object of our invention, therefore, to provide a syringe which is constructed such that, once it is used with a patient, it can be easily and safely manipulated by medical personnel to break the syringe and retract the cannula entirely within the barrel of the syringe such that the cannula point will not thereafter be available to injure anyone including the medical personnel further handling the syringe. Our invention is noteworthy because it is economical to produce and will not substantially increase the cost of a syringe.
It is a further object of our invention to provide such a syringe comprising a barrel having a proximal end and a distal end, a plunger reciprocably disposed in the barrel to drive fluid from the distal end when moving in that direction and end wall means for closing the distal end of the barrel. The end wall means may preferably be formed as a part of the syringe barrel with a defined frangible portion designed to be broken by the pushing action of the plunger after the contents have been fully injected A cannula may be mounted on the end wall means for the barrel in a conventional manner Then, we provide means for connecting the end wall means to the plunger such that, movement of the plunger toward the proximal end will move the end wall means and cannula within the barrel to what we refer to as a point protective position.
It is still another object of our invention to provide such an end wall means which includes an annular frangible portion providing a connection between the end wall means and the barrel This frangible portion will be broken when the plunger is pushed toward the barrel distal end with a pushing force significantly higher than required to inject the contents of the syringe. The plunger may preferably be proportioned and shaped to have an annular shoulder to engage and break the annular frangible portion when the plunger is pushed toward the distal end a predetermined amount beyond that required fully to inject the contents.
The following objects further summarize the advantages of our invention:
To provide an improved anti-needle stick, anti-drug abuse syringe which uses industry standard cannula fixtures in which the cannula point is retracted into the barrel of the syringe after use of the syringe, and in which the syringe is no longer useful after its initial use.
To provide such a syringe in which the cannula is locked in its point protective position within the barrel.
To provide such a syringe which requires little additional manipulation to properly operate the syringe, relative to conventional syringes.
To provide such a syringe which may be used in pre-filled and non-filled applications. To provide such a syringe which allows multiple needles to be mounted and used during a single use of the syringe. In some applications, for example, a relatively large diameter needle is used to draw product into the syringe, this larger needle is removed and disposed of and replaced with a needle of relatively small diameter, and product is injected in one or more injections using this smaller needle. It should be noted that the first needle is used only to draw product into the syringe and is not therefore contaminated.
To provide such a syringe which has a smooth inner bore to eliminate air entrapment and provides a reliable means of expelling air which may have been introduced during filling.
To provide such a syringe which allows for substantially complete injection of fluid, minimizing waste of and improving accuracy of measurement of product.
To provide such a syringe which has minimal part count to improve ease of manufacture and sterility.
To provide such a syringe which has substantial means of preventing unintentional recantation of needle, as during impingement with bone or other hard materials.
To provide such a syringe in which the plunger may move through the barrel to deliver the product in a smooth, controlled motion without sudden movement or jarring of the needle which might alarm the patient or damage tissue Such sudden movement or jarring might be caused, for example, by a snap fitting which is sometimes used as a means for engaging the needle or closing means with the plunger or retracting means.
To provide such a syringe in which the operator of the syringe receives tactile feedback indicating complete injection.
To provide such a syringe in which the syringe must be manipulated in an intentional manner in order to separate the end wall means from the barrel.
Other objects, features, and advantages of the present invention will become apparent as this specification progresses.